Combination of dopamine agonists plus first phase insulin secretagogues for the treatment of metabolic disorders

ABSTRACT

The present invention is directed to a method of treating a metabolic disorder or key elements of a metabolic disorder such method comprising the use of an agent(s) that increases central dopaminergic activity plus a first-phase insulin secretagouge.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of and claims priority to U.S.application Ser. No. 13/375,810, filed on Feb. 23, 2012, which is a 371of International Application No. PCT/US2010/037605 filed on Jun. 7, 2010which, in turn, claims benefit of Provisional U.S. Application Ser. No.61/217,906 filed on Jun. 5, 2009. The contents of the prior applicationsare incorporated herein by reference in their entireties.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is directed to agents that increase centraldopaminergic activity plus first phase insulin secretagogues for thetreatment of metabolic disorders.

2. Description of the Related Art

Type 2 diabetes (T2D) is characterized by both an ineffectiveness ofinsulin to maintain normal plasma glucose levels because of resistanceof the body to its normal action to induce removal of glucose from thecirculation into insulin sensitive tissues when glucose is abnormallyhigh such as after consumption of a meal and also by beta cell failureto secrete appropriate amounts of insulin particularly following ameal/glucose challenge. This insulin resistance coupled with beta cellfailure results in abnormally high circulating plasma glucose levels andis coupled with a myriad of other metabolic disorders such asdyslipidemia and hypertension that collectively predispose tocardiovascular disease, the leading cause of death in the T2D patient.Type 2 diabetes is now a global pandemic with more than 200 millionpeople affected with the disease and the World Health Organizationestimates that by 2030 there will be approximately 300 million peoplewith the disease world-wide. Additionally, a condition termedpre-diabetes is also growing globally with approximately twice thenumber of affected individuals as type 2 diabetes. The definition ofpre-diabetes varies among health organizations but is generallyclassified as Impaired Fasting Glucose (IFG) (fasting glucose levelsbetween 110-125 mg/dl) or Impaired Glucose Tolerance (IGT) (2-hour postoral glucose load (75 g) plasma glucose greater than 140 to 199 mg perdL (7.8 to 11.0 mmol)) and is accompanied by an increased risk for thedevelopment of frank T2D. IFG and IGT are distinct metabolicabnormalities (Abdul-Ghani M A et al, Diabetes 55:1430-35, 2006). It nowappears that the 1-hour post glucose load plasma glucose level is abetter predictor of future T2D onset than IFG or IGT (Abdul-Ghani M A etal, Diabetes Care 32:281-86, 2009). Indeed in subjects with fastinghyperglycemia and a normal 2-hour post-glucose load plasma glucoselevel, it is the 1-hour plasma glucose that is most predictive of futureT2D onset (Abdul-Ghani M A et al, Diabetes Care 33:557-561, 2010).Insulin secretory response to an oral glucose load is typically composedof a first-phase and second phase response. Insulin is released from thepancreas in a biphasic manner in response to a square-wave increase inarterial glucose concentration. The first phase consists of a briefspike lasting about 10 min followed by the second phase, which reaches aplateau at 2-3 h. It is widely thought that diminution of first-phaseinsulin release is the earliest detectable defect of β-cell function inindividuals destined to develop type 2 diabetes and that this defectlargely represents β-cell exhaustion after years of compensation forantecedent insulin resistance. Subjects with IGT are characterized byimpaired first and second phase insulin secretory response whilesubjects with IFG are characterized mainly by impaired first phaseinsulin secretory response (Abdul-Ghani M A et al, Eur J Clin Invest inpress; Ferrannini E et al, Diabetologia 46: 1211-1219, 2003). Subjectswith T2D have impairments in both phases of insulin secretion. Subjectswith IFG, IGT and T2D all have insulin resistance. Postprandial glucosedysmetabolism (elevated postprandial glucose levels; postprandialhyperglycemia) has been identified as a risk factor not only forprogression to T2D but also for cardiovascular disease (CVD) (Bonora Eet al, Diabetologia 44:2107-14, 2001; Ceriello A et al, Nutr MetabCardiovasc Dis 16:453-6, 2006; Di Filippo C et al, Curr Diabetes Rev3:268-73, 2007). Therefore postprandial hyperglycemia is important tocorrect in the prediabetes and T2D subjects alike to improve overallmetabolic and cardiovascular health. Little attention has been given tomethods of treating postprandial insulin resistance however and littleis known of what controls this postprandial insulin response in themuscle and liver. There are currently no methods of treatment availablethat improve postprandial insulin resistance and first phase insulinsecretory response in subjects with prediabetes or T2D. The ability tocorrect both of these abnormalities would likely lead to betterpostprandial glucose control and health outcomes in subjects with IFG,IGT and T2D. What is needed is a simple method of treating bothpostprandial insulin resistance and first-phase insulin secretion as amethod of improving IFG, IGT and T2D.

SUMMARY OF THE INVENTION

It has recently been determined that timed once daily administration ofcentrally acting dopamine agonists (such as bromocriptine) or ofcompounds that increase central dopaminergic activity particularly atthe appropriate time of day when central/hypothalamic dopaminergicactivity is high in insulin sensitive non-T2D subjects and low in suchsubjects, improves postprandial glucose metabolism (FDA Cycloset®package insert 2009) without increasing insulin release. This suggeststhat such dopamine agonist treatment may improve postprandial insulinresistance. It has now been surprisingly found that if one combines sucha method of treating 1FG, 1GT, or T2D with a first-phase insulinsecretagogue, one can produce synergistic effects to reduce thesedisorders. Additional dopamine agonists useful in the invention includequinpirole, quinerolane, talipexole, ropinirole, apomorphine, lisuride,terguride, fenoldopam, dihydroergotoxine, (hydergine),dihydroergocryptine, and combinations thereof. A most preferred centralacting dopamine agonist is bromocriptine.

Cycloset, a quick-release, high absorbing formulation of bromocriptinemesylate, a dopamine agonist, improves glycemic control in type 2diabetes in large part by improving postprandial responsiveness toinsulin. Several drugs that directly or indirectly stimulate an increasein first phase insulin release (termed first phase insulinsecretagogues) also produce improvements in glycemic control by loweringpostprandial glucose levels in subjects with type 2 diabetes.

We have now found that improved glycemic control in subjects with type 2diabetes is possible by combining these two different drug classes,e.g., agents that increase central dopamine activity plus first phaseinsulin secretagogues as defined herein. The combination of suchdopamine activity regulating agents and first phase insulin secretagoguehas been observed to have advantageous effects. First, the combinationproduces more than additive, i.e., synergistic, effects on glycemiccontrol. This synergism may also be realized with dopamine agonists,such as Cycloset and short acting insulins. Secondly, the combinationpermits one to reduce the daily dosages of Cycloset and the insulinsecretagogue and get additional benefit on glycemic control whencombined at these lower dosages relative to their regular respectivesingle dosage uses. Thirdly, the combination reduces overall sideeffects of each of these agents. Fourth, the metabolic benefits ofimprovements in lipid metabolism, blood pressure, and vasculardysfunction, and heart and kidney disease may also be realized in asimilar synergistic manner with this agent increasing centraldopaminergic activity—first phase insulin secretagogue drug combination.In total, this unique combination allows for synergistic increasedeffectiveness and simultaneous decreased side effects for treatingmetabolic disease at lower doses than each drug class is utilized atindividually to treat such metabolic disorders.

The combination composition is effective to treat one or more metabolicdisorders selected from the metabolic syndrome, Type 2 diabetes,obesity, prediabetes, key elements of any metabolic disorder, insulinresistance, hyperinsulinemia, cardiovascular disease, elevated plasmanorepinephrine, elevated cardiovascular-related inflammatory factors orpotentiators of vascular endothelial dysfunction, hyperlipoproteinemia,atherosclerosis, hyperphagia, hyperglycemia, hyperlipidemia,hypertension, and high blood pressure. The key elements of a metabolicdisorder is selected from the group consisting of impaired fastingglucose, impaired glucose tolerance, increased waist circumference,increased visceral fat content, increased fasting plasma glucose,increased fasting plasma triglycerides, increased fasting plasma freefatty acids, decreased fasting plasma high density lipoprotein level,increased systolic or diastolic blood pressure, increased plasmapostprandial triglyceride or free fatty acid levels, increased cellularoxidative stress or plasma indicators thereof, increased circulatinghypercoagulative state, arteriosclerosis, coronary artery disease,peripheral vascular disease, congestive heart failure, hepaticsteatosis, renal disease including renal insufficiency, andcerebrovascular disease.

First phase insulin secretagogues include but are not limited to aglucagon-like peptide-1 (GLP-1) or mimetic thereof, insulin and/or ameglitinide, repaglinide, nateglinide or a dipeptidyl peptidaseinhibitor.

Multiple circadian central neural oscillations govern the regulation andcoordination of multiple physiological (e.g., metabolic) events in theperiphery as a function of their circadian (timing) phase relationship,described in U.S. Pat. No. 5,468,755 and herein incorporated in entiretyby reference. One such circadian rhythm governing metabolic status isthe central (hypothalamic) circadian rhythm of dopaminergic activity. Ithas previously been observed that phase shifts in the circadian rhythmof central dopaminergic activities influenced the status of obesity ordiabetes. However, it has now been surprisingly found that phase shiftsaway from the healthy normal circadian rhythm of central or hypothalamicdopaminergic activity by environment, diet, stress, genetics and/orother factors are somehow also operative in a much different and broaderphysiological regulatory system and potentiate and lead to the multiplecomplex metabolic pathologies of and associated with metabolic syndromeas described herein. Furthermore, it has now been found that resettingthese aberrant central dopaminergic circadian rhythms back towards thatof the healthy normal state results in simultaneous improvements in themultiple complex pathologies of and associated with metabolic syndromeas described herein. As described above, metabolic syndrome and itsassociated pathologies represent a different pathology from diabetes orobesity, the cause of which is unknown. However, subjects with metabolicsyndrome have much greater risk of developing cardiovascular diseasethan subjects without the syndrome. Inasmuch as obesity and type 2diabetes are not always associated with metabolic syndrome and viceversa, it is clear that this major health risk represents a separate andunique metabolic state with unique characteristics. Adjusting thecircadian rhythm of central dopaminergic activities by various means maybe employed to reduce the many pathologies of and associated with thissyndrome, for example aberrant vascular tone, vascular health,endothelial function, glucose and lipid metabolism, immune systemfunctions specifically influencing the vasculature, insulin action, andblood coaguability. This same circadian dopaminergic resettingmethodology may also be utilized to treat cardiometabolic risk, acluster of physiological pathologies of common or discordant origin thatconverge to increase risk of cardiovascular disease. These risk factorsinclude those of metabolic syndrome, but also inflammation, endothelialdysfunction, hypercholesterolemia, diabetes, obesity, smoking, gender,and age. Rather than just increasing dopaminergic activity with centraldopamine agonists to improve metabolic syndrome, cardiometabolic riskand their associated pathologies, one may better influence theseconditions by timing the administration of such dopamine agonists tocoincide with the daily peak in central dopaminergic activities ofhealthy subjects of the same species to derive maximal benefit from suchdopamine agonist therapy in treating these conditions.

In further accordance with this invention, the use of dopamine agoniststo treat the Metabolic Syndrome (obesity, insulin resistance,hyperlipidemia, and hypertension), non-metabolic pathologies associatedwith MS (a pro-inflammatory state, a pro-coagulative state, pro-oxidantstate, and/or endothelial dysfunction), arteriosclerosis, and/orcardiovascular disease, all in subjects with or without Type 2 diabetes,is applied during specific daily intervals to maximize the effectivenessof such treatment. Use of such centrally acting dopamine agonists fortreatment of the metabolic and non-metabolic vascular disordersdescribed herein may be potentiated by their administration at theappropriate time(s) of day. Circadian rhythms of dopaminergic activitywithin the central nervous system, and particularly the phase relationsof these dopaminergic neuronal rhythms with other circadian neuronalactivities such as serotonergic neuronal activities have beendemonstrated to regulate peripheral glucose and lipid metabolism in amanner dependent upon the phase of the daily peak in circadian centraldopaminergic activity. Consequently, increases in dopaminergic activityat particular times of day versus others produce maximal effectivenessin improving metabolic diseases and disorders such as type 2 diabetes,obesity, pre-diabetes, metabolic syndrome, cardiometabolic risk,hypertension, dyslipidemia, insulin resistance, hyperinsulinemia,hepatic steatosis, renal disease, cardiovascular disease,cerebrovascular disease, and peripheral vascular disease and biomarkersof impending vascular disease. As such, maximized successful treatmentof these aforementioned pathologies and abnormalities may beaccomplished by appropriately timed daily administration of centrallyacting dopamine agonist(s). Because such dopamine agonist therapyattacks a root cause of these metabolic disorders (central dysregulationof global peripheral metabolism) it is possible to effectuateimprovements in several metabolic pathologies in a simultaneous fashionthat is not generally achievable by other conventional means that attackparticular specific symptoms of metabolic disease for examplehypertension or high cholesterol or hyperglycemia by acting at specificdownstream peripheral targets such as biochemical pathways within liveror muscle. Such a treatment effect is currently lacking in the generalarmamentarium of therapeutics for metabolic diseases. Moreover, centraldopamine agonist therapy may be coupled to direct or indirect peripheralacting therapeutic agents such as anti-diabetes agents, antihypertensiveagents, cholesterol lowering agents, anti-inflammatory agents, oranti-obesity agents to produce additive improvements in metabolicdisease such as obesity or type 2 diabetes or particular aspects ofmetabolic disease such as hypertension associated with obesity or type 2diabetes. Details of the timing aspects of the invention can be found incopending International Patent Application Publications WO 2008/150480and WO 2008/121258.

The novel treatment for metabolic disorders, including the metabolicsyndrome (obesity, insulin resistance, hyperlipidemia, andhypertension), Type 2 diabetes, obesity, and/or prediabetes includingkey elements of metabolic disorders consists of administering to amammalian species in need of such treatment a pharmaceutical compositionthat simultaneously stimulates an increase in central dopaminergicneuronal activity level (particularly within neurons innervating thehypothalamus and the hypothalamus itself) and a decrease in centralnoradrenergic neuronal activity level (particularly within the brainstem region that innervates the hypothalamus and the hypothalamusitself). It has been unexpectedly discovered that increasing the ratioof dopaminergic neuronal to noradrenergic neuronal activity within thecentral nervous system, particularly the hypothalamus of the centralnervous system reduces metabolic disorders and improves the conditionsassociated with metabolic syndrome, type 2 diabetes, obesity, and/orprediabetes and key elements thereof. As defined herein, “neuronalactivity” refers to either an increase or decrease in the actionpotential of a neuron. More specifically, as defined herein, “neuronalactivity” refers to either an increase or decrease in the synapticneurochemical signal transmission of a neuron to another therebyaffecting action potential. More narrowly yet, as defined herein,“neuronal activity” refers to the biochemical communication to a(secondary [e.g., post-synaptic]) neuron from either the neurochemicalsignal transmission of another (primary [e.g., pre-synaptic]) neuron(e.g., as via an endogenous neurotransmitter) or from anyneuromodulatory compound (e.g., an exogenous neurotransmitter receptormodulator such as a pharmaceutical agent) thereby affecting actionpotential or neurotransmitter release of the secondary neuron. As such,an increase in dopaminergic neuronal activity would be characterized bya) an increase in release of dopamine molecules from a dopamineproducing (primary) neuron, an increase in dopamine molecules within thesynapse by any mechanism, and/or increase in dopamine-mimeticcompound(s) from any source (e.g., pharmaceutical) resulting inincreased binding to dopaminergic receptor sites of other (secondary)neuron(s) that affect said other neuron(s)′ action potential orneurotransmitter release in a manner consistent with increased dopamineligand-dopamine receptor binding signal transduction (e.g.,post-synaptic dopamine receptor agonist) and/or b) an increase insensitivity or responsiveness of said “other (secondary)” neuron(s) tosuch dopamine or dopamine-mimetic compound(s)′ ability to affect actionpotential or neurotransmitter release in said “other (secondary)” neuron(e.g., as an increase in dopamine receptor number or affinity orresponsiveness). Contrariwise, dopamine-mimetic binding todopamine-producing neurons (i.e., presynaptic dopamine neurons) and/orincreased sensitivity or responsiveness of dopamine producing neurons torespond to neurotransmitters or neuromodulators that thereby reducesdopamine release would be considered an activity leading to a decreasein dopaminergic neuronal activity [and, when considered in and ofitself, is an undesirable aspect of dopaminergic activity respectingthis invention]. For the sake of clarity, post-synaptic dopaminereceptor agonists include dopamine D1, D2, D3, D4, and D5 receptoragonists and post-synaptic norepinephrine receptor antagonists includealpha 2bc and alpha1 antagonists.

DETAILED DESCRIPTION OF THE INVENTION Materials and Methods

Animal Studies

Male Syrian hamsters known to develop insulin resistance and glucoseintolerance were purchased at 4 weeks of age and kept on rodent diet for10 weeks at 72 degrees F. and a 14 hr:10 hr daily light:dark cycle. Whenanimals were 14 weeks of age on this daily photoperiod (known to beinsulin resistant and glucose intolerant under these conditions),bromocriptine mesylate was administered intraperitoneally (IP) for 2weeks at 4 mg/kg per hamster 13 hours after light onset to half of theanimals, while the other half received vehicle injections for 2 weeks.

After 2 weeks of treatment both Bromocriptine and vehicle groups weredivided into two groups for a total of 4 groups: 1. Vehicle for 2 weeksand Vehicle at initiation of a glucose tolerance test (GTT); 2. Vehiclefor 2 weeks and Exendin-4 at initiation of the GTT; 3. Bromocriptine for2 weeks and Vehicle at GTT; 4. Bromocriptine for 2 weeks and Exendin-4at GTT.

Glucose tolerance test was performed among all 4 study groups on Day 15of the study by challenge with 3 g/kg body weight of glucose at 7 hoursafter light onset among each of the 4 treatment groups—(bromocriptine orvehicle treatment for 2 weeks and with IP injection of either vehicle or4 μg/kg of Exendin-4, a GLP-1 analog [Sigma Chemical, St Louis, Mo.]dissolved in saline) at the GTT. Also, an additional group of hamsterstreated with vehicle for 2 weeks received Exendin-4 on the day of GTT at8 μg/kg. Blood was drawn from the jugular vein and blood glucose levelwas measured every 30 minutes for 2 hours after the glucose loadadministration.

In a similarly designed experiment among 4 groups of animals, insulinwas injected IP at 240 ng/kg in place of Exendin-4 as the first phaseinsulin secretagogue (FPIS).

Human Studies

494 obese Type 2 diabetes subjects who were poorly controlled on asulphonylurea dose that was stable for at least 60 days prior to studyinitiation were enrolled in a multicentre study, with 244 randomized totreatment with Cycloset plus a stabilized dose of currently usedsulphonylurea, and 250 randomized to treatment with placebo plus astabilized dose of currently used sulphonylurea. Subjects were admittedto a clinical research center one week prior and 24 weeks after thestart of Cycloset administration and administered standardized meals atbreakfast lunch and dinner. One-hour postprandial plasma insulin andglycated hemoglobin A1c (HbA1c) (a measure of glycemic control) weremeasured one week prior and 24 weeks after the start of Cyclosetadministration. Cycloset induced improvements in HbA1c relative toplacebo were analyzed as a function of the baseline 1-hour postprandialinsulin level in the study subjects.

Results

Animal Studies

Timed Bromocriptine administration for 2 weeks did not statisticallysignificantly reduced blood glucose Area Under Curve (AUC) during theGTT over two hours after glucose administration (21% reduction, P<0.09).Likewise Exendin-4 immediately prior to glucose administration at either4 ug/kg or 8 ug/kg did not statistically significantly reduced bloodglucose Area Under Curve (AUC) during the GTT over two hours afterglucose administration (19% and 27% reduction, P=0.23 and P=0.13respectively). However, in animals that were treated both withbromocriptine for 2 weeks and received Exendin-4 at 4 ug/kg prior to GTTinitiation a statistically significant decrease of Glucose AUC of 60%was observed (P<0.0002). Thus no statistically significant effect ofeither the dopamine agonist treatment or of the first-phase insulinsecretagogue on glucose intolerance was observed, yet the combination ofthe two produced a marked improvement in glucose intolerance, thenumerical value of which was 50% greater than the addition of the twodrug effects separately and also more than double the effect of doublingthe dose of exendin-4 (P=0.05). Even when viewed in these terms, a 50%reduction in the GTT AUC represents a robust improvement in relativeglucose intolerance (Ceriello A et al Nutr Metab Cardiovasc Dis16:453-6, 2006; Abdul-Ghani M A et al, Diabetes Care 32: 281-86, 2009).This synergistic effect of these agents (0+0=marked effect) allows forthe lowering of the first-phase insulin secretagogue (FPIS) dose and yetto achieve better results when combined with a centrally acting dopamineagonist (as evidenced by the result that 2× the Exendin-4 dose did notproduce any benefit to glucose intolerance and was not even half thenumerical effect of the dopamine agonist/half FPIS dose on glucoseintolerance). The lowering of the FPIS allows for reducing its sideeffects and strain on the beta cell (beta cell exhaustion) which isbeneficial to the treated subject.

In a similarly designed experiment as above but replacing the FPIS fromexendin-4 to exogenous insulin itself, glucose AUC over two hours aftersuch glucose administration was not significantly reduced by 2 weeks oftreatment with bromocriptine (28% reduction, P=0.23) or by insulinadministration immediately prior to glucose administration (P=0.64).However, animals that were both treated with Bromocriptine for 2 weeksand received insulin prior to the GTT exhibited a decrease of GlucoseAUC of 55% (P=0.014). Once again, the combination of a FPIS (insulin)plus a central acting dopamine agonist produces an effect much greaterthan the sum of the individual treatments as each were ineffective inproducing any beneficial result. Once again, even when viewed innumerical terms irrespective of statistical significance, thecombination produced a reduction in glucose intolerance of 50% greaterthan the addition of each therapy alone which as stated above is amarked improvement in glucose intolerance with demonstrable healthbenefits.

The observation that this synergism is achieved with 2 markedlydifferent FPIS molecules that share only the ability to increase plasmainsulin level after a meal when administered prior to the meal indicatesthat this is a class phenomenon and not something particular to the FPISagents employed. Previously it has been demonstrated that various agentsthat increase central dopaminergic activity all improve metabolicdisorders, again indicating that the phenomenon, in a general sense, isnot molecule specific, but rather a class effect. Therefore, thissynergism may be fully expected to be a class interaction synergism.

Inasmuch as meals for humans are typically 3 times per day, it ispossible to reduce this combination synergistic therapeutic formetabolic disorders to a once-daily dosing by preparing long acting FPISwith short acting agents that increase central dopaminergic activity atspecific time of day only in unique dosage forms. Such dosage formsprovide the benefit of the synergism, allow for the maximal effect ofthe dopamine stimulation by timing it to the appropriate time of day,and provide for convenience of use (only a single administration perday). Such dosage forms may take the form of non-oral or oral routes ofadministration.

Human Studies

The average 1-hour postprandial plasma insulin level was 50 μU/ml inboth Cycloset and Placebo treated groups at the start of the study;incoming HbA1C was 9.4% and 9.5% respectively. In the Cycloset treatedgroup HbA1C was reduced by 0.3% over 24 weeks of treatment, while HbA1Cwent up by 0.26% in the Placebo arm (P<0.0001). For subjects withincoming 1-hour postprandial insulin <30 uU/ml there was no effect ofCycloset on HbA1c, for subjects with incoming 1-hour postprandial >30uU/ml and <50 uU/ml the Cycloset effect was −0.57 (P<0004) and amongsubjects with incoming 1-hour postprandial insulin >50 μU/ml theCycloset effect on HbA1C was −0.79 (P<0.0001).

These results indicate that the effect of the dopamine agonist toimprove glycemic control in T2D subjects is positively correlated with1-hour postprandial insulin level in the subjects supporting the conceptthat the combination of an agent that increases central dopaminergicactivity with a FPIS will produce synergistic improvements in glucosemetabolism. Moreover the collective results of these animal and humanstudies indicate that pharmaceutical agents that preserve pancreaticbeta cell function per se, i.e., retard the loss of appropriate betacell insulin responsiveness to meal glucose (and as such improvepostprandial insulin secretory response to glucose) such asthiazolidinediones and glucagon like peptide 1 analogs, will alsosynergize with agents that increase central dopaminergic activity toimprove metabolic disorders and produce long lasting benefit on glycemiccontrol (e.g., for a year or more). This combination of therapies forthe treatment of metabolic disorders is also envisioned by thisinvention as well.

Exendin-4

Exendin-4, a 39 amino acid peptide, originally isolated from Helodermasuspectum (Gila monster lizard) venom, activates GLP-1 (glucagon-likepeptide-1) receptors to increase intracellular cAMP in pancreatic acinarcells. Synthetic Exendin-4 is also known as Exenatide, or Byetta; itsmolecular weight is: 4187.

GLP-1 is a gastrointestinal hormone, which regulates blood glucoseprimarily by stimulating glucose-dependent insulin release (first phaseinsulin secretion). Exendin-4 is a high affinity glucagon-like peptide 1(GLP-1) receptor agonist (Kd=136 μM). Exendin-4 is a long-acting agonistof the GLP-1 receptor. Exenatide has comparable potency to GLP-1 and isresistant to degradation by DPP-IV. Exenatide improves glycemic controlprimarily by reducing postprandial hyperglycemia.

Exendin-4 dose used in this study is comparable to the dose used in thestudies reported by Strauss et al., 2008 and Nachnani et al., 2010.

REFERENCES

-   Cervera et al., (2008) Mechanism of action of exenatide to reduce    postprandial hyperglycemia in type 2 diabetes. Am J Physiol    Endocrinol Metab 294: E846-E852.-   Eng, J. et al., (1992) Isolation and characterization of exendin-4    an exendin-3 analogue from Heloderma suspectum venom. J. Biol. Chem.    267, 7402.-   Goke et al (1993) Exendin-4 is a high potency agonist and truncated    exendin-(9-39)-amide an antagonist at the glucagon-like peptide    1-(7-36)-amide receptor of insulin-secreting b-cells. J. Biol. Chem.    268 19650.-   Nachnani J. et al., (2010) Biochemical and histological effects of    exendin-4 (exenatide) on the rat pancreas. Diabetologia 53:153-159.-   Thorens et al (1993) Cloning and functional expression of the human    islet GLP-1 receptor. Diabetes 42 1678.-   Strauss A. et al., (2008) Exendin-4 improves the oral glucose    tolerance in diabetic rats: pancreas regeneration, better function    of pancreatic islets, or impaired glucose uptake? Transplantation    Proceedings, 40, 533-535

What is claimed is:
 1. A method of treating a metabolic disorder or keyelements of a metabolic disorder such method comprising the step ofadministering to a patient having a metabolic disorder or a patient inneed thereof, (a) a dopamine receptor agonist; and (b) a first-phaseinsulin secretagogue selected from the group consisting of glucagon likepeptide-1 (GLP-1) or an analog thereof, a dipeptidyl peptidaseinhibitor, gastric inhibitory polypeptide (also known asglucose-dependent insulinotropic peptide), a meglitinide, repaglinide,nataglinide and short acting insulin, wherein the dosage of each of saiddopamine receptor agonist and first-phase insulin secretagogue incombination, provides a therapeutic effect greater than the additiveeffect of administering the same dosage of each of said dopaminereceptor agonist and first-phase insulin secretagogue alone and whereinthe dopamine receptor agonist is administered so as to increase centraldopaminergic activity at the time of day its circadian rhythm naturallypeaks in healthy subjects of the same species and said first phaseinsulin secretagogue is administered such that an effective amount ispresent daily.
 2. The method of claim 1, wherein the dopamine receptoragonist is selected from the group consisting of bromocriptine,lisuride, hydergene, dihydroergotoxine, and other dopamine D2 receptoragonists with low or no serotonin 2B receptor agonist activity.
 3. Themethod of claim wherein metabolic disorder is selected from the groupconsisting of pre-diabetes, Impaired Fasting Glucose, Impaired GlucoseTolerance and Type 2 diabetes.
 4. The method of claim wherein themetabolic disorder is selected from the group consisting of themetabolic syndrome, Type 2 diabetes, obesity, prediabetes, insulinresistance, hyperinsulinemia, cardiovascular disease, elevated plasmanorepinephrine, elevated cardiovascular-related inflammatory factors orpotentiators of vascular endothelial dysfunction, hyperlipoproteinemia,atherosclerosis, hyperphagia, hyperglycemia, hyperlipidemia,hypertension, and high blood pressure.
 5. The method of claim whereinthe key elements of metabolic disorders are selected from the groupconsisting of impaired fasting glucose, impaired glucose tolerance,increased waist circumference, increased visceral fat content, increasedfasting plasma glucose, increased fasting plasma triglycerides,increased fasting plasma free fatty acids, decreased fasting plasma highdensity lipoprotein level, increased systolic or diastolic bloodpressure, increased plasma postprandial triglyceride or free fatty acidlevels, increased cellular oxidative stress or plasma indicatorsthereof, increased circulating hypercoagulative state, arteriosclerosis,coronary artery disease, peripheral vascular disease, congestive heartfailure, hepatic steatosis, renal disease including renal insufficiency,and cerebrovascular disease.
 6. The method of claim wherein saiddopamine receptor agonist is administered to a human to increase centraldopaminergic activity primarily within 4 hours of waking in the morning.7. The method of claim wherein said dopamine receptor agonist isadministered within 2 hours of waking in the morning.
 8. The method ofclaim 1, wherein the dosage of the dopamine receptor agonist isinsufficient to effectively treat said disorder or key elements of saiddisorder without co-administration of the first-phase insulinsecretagogue.
 9. The method of claim 1, wherein the dosage of thefirst-phase insulin secretagogue is insufficient to effectively treatsaid disorder or key elements of said disorder without co-administrationof the dopamine receptor agonist.
 10. The method of claim 1, wherein thedosage of each of the dopamine receptor agonist and the first-phaseinsulin secretagogue in combination are effective to treat said disorderor key elements of said disorder.
 11. The method of claim 1, wherein thedopamine receptor agonist is selected from the group consisting ofquinpirole, quinerolane, talipexole, ropinirole, apomorphine, terguride,fenoldopam, dihydroergocryptine and combinations thereof.
 12. The methodof claim wherein the dosage of said first-phase insulin secretagogueeffective to treat said disorder when administered with said dopaminereceptor agonist is less than the dosage of said secretagogue effectiveto treat said disorder when administered without said dopamine receptoragonist.
 13. The method of claim 1, wherein the dopamine receptoragonist is a combination of a dopamine D1 receptor agonist and adopamine D2 receptor agonist.
 14. A method of treating glucoseintolerance or insulin resistance in a mammal in need of such treatment,such method comprising: administering to a mammal suffering from glucoseintolerance (a) a dopamine D2 receptor agonist selected from the groupconsisting of bromocriptine, lisuride, hydergene, dihydroergotoxine, andother dopamine D2 receptor agonists with low or no serotonin 2B receptoragonist activity; and (b) a first-phase insulin secretagogue selectedfrom the group consisting of glucagon like peptide-1 (GLP-1) or ananalog thereof, a dipeptidyl peptidase inhibitor, gastric inhibitorypolypeptide (also known as glucose-dependent insulinotropic peptide), ameglitinide, repaglinide, nataglinide and short acting insulin, whereinthe dosage of each of said dopamine D2 receptor agonist and first-phaseinsulin secretagogue in combination provides a therapeutic effectgreater than the additive effect of administering the same dosage ofeach of said dopamine D2 receptor agonist and first-phase insulinsecretagogue alone and wherein the dopamine receptor agonist isadministered so as to increase central dopaminergic activity at the timeof day its circadian rhythm naturally peaks in healthy subjects of thesame species and said first phase insulin secretagogue is administeredsuch that an effective amount is present daily.
 15. The method of claim14, wherein the mammal suffers from diabetes or pre-diabetes.
 16. Amethod of treating glucose intolerance or insulin resistance in a mammalin need of such treatment, such method comprising: administering to amammal suffering from glucose intolerance or insulin resistance (a)bromocriptine or a pharmaceutically acceptable salt thereof; and (b) afirst-phase insulin secretagogue selected from the group consisting ofGLP-1 or an analog thereof and insulin, wherein the dosage of each ofbromocryptine or a pharmaceutically acceptable salt thereof andfirst-phase insulin secretagogue in combination, provides a therapeuticeffect greater than the additive effect of administering the same dosageof each of said bromocriptine or a pharmaceutically acceptable saltthereof and said first-phase insulin secretagogue alone and wherein thebromocryptine or a pharmaceutically acceptable salt thereof isadministered to increase central dopaminergic activity at the time ofday its circadian rhythm naturally peaks in healthy subjects of the samespecies and said first phase insulin secretagogue is administered suchthat an effective amount is present daily.
 17. The method of claim 16,wherein the salt is mesylate.
 18. The method of claim 16, wherein themammal is suffering from type 2 diabetes.
 19. A method of treating ametabolic disorder or key elements of a metabolic disorder such methodcomprising the step of administering to a patient having a metabolicdisorder or a patient in need thereof, (a) a dopamine receptor agonist;and (b) a first-phase insulin secretagogue selected from the groupconsisting of glucagon like peptide-1 (GLP-1) or an analog thereof, adipeptidyl peptidase inhibitor, gastric inhibitory polypeptide (alsoknown as glucose-dependent insulinotropic peptide), a meglitinide,repaglinide, nataglinide and short acting insulin, wherein the dosage ofeach of said dopamine receptor agonist and first-phase insulin incombination, provides a therapeutic effect greater than the additiveeffect of administering the same dosage of each of said dopaminereceptor agonist and first-phase insulin secretagogue alone and whereinsaid dopamine receptor agonist and said first phase insulin secretagogueare administered such that an effective amount of each is present daily.